The invention relates to a clutch disc for a motor vehicle clutch including a carrier plate connected with an elastomer intermediate layer that is connected with a clutch lining, with the elastomer intermediate layer being essentially composed, as taught by EP 0,351,447, of hydrated nitrile rubber (HNBR) and/or a fluoroelastomer (FPM). By way of a composite binder, the elastomer intermediate layer is connected with the adjacent layers by chemical sorption. The elastomer layer acts as a spring and imparts to the clutch disc an elasticity with a non-linear spring characteristic in a direction perpendicular to the plane of the clutch disc. The connecting faces between the elastomer intermediate layer and the adjacent layers are smaller than the faces of the adjacent layers facing the intermediate layer (partial congruence).
The basic characteristics of such a clutch disc are disclosed in EP 0,351,447. Compared with prior art clutch discs, this disc is particularly distinguished in that an elastomer intermediate layer is provided instead of the steel springs that are otherwise riveted to the friction linings, thus enabling the clutch linings to be made a few millimeters thinner since, due to the absence of rivets, they can be worn down completely. Nevertheless, this clutch disc is able to withstand all demands made on it during operation, particularly with respect to stressability also under heat, wetness, etc., because, according to the cited patent, the elastomer intermediate layer is connected with the adjacent layers by means of chemical sorption.
In this European patent it is also proposed to impart a defined non-linear spring characteristic to the elastomer intermediate layer in that the faces are only partially congruent. That means, the elastomer intermediate layer is made smaller than the two layers adjacent to it and connected with it.
An English-language translation of the entire specification of EP 0,351,447 is reproduced at the end of this "Background" section.
In connection with the prior art, reference is also made to U.S. Pat. No. 1,898,978 which already discloses a clutch disc whose friction coating is provided with notches that extend ray-like essentially in the radial direction of the lining. However, the clutch lining is here contiguous and the notches are provided to reduce the noise developed during engagement of the clutch. They are not intended to impart a defined non-linear spring characteristic to the clutch disc, and they are unable to do this since they are attached in an essentially non-elastic material, namely in the actual clutch lining.
Similar prior art is disclosed in U.S. Pat. No. 2,097,710 where the carrier sheets of the clutch discs disclosed there are corrugated in some embodiments and the clutch lining is provided with radially extending grooves. Here again, it is not possible nor intended to impart a predetermined spring characteristic to a clutch disc.